Certain kinds of tetrahydrophthalimide derivatives such as 2-[7-fluoro-4-(2-propynyl)-2H-1,4-benzoxazin-3(4H)-on-6-yl]-4,5,6,7-tetrah ydroisoindole-1,3-dione are known as agrochemicals having a herbicidal activity. It is also known that these derivatives can be produced from benzoxazine compounds of the general formula: ##STR2## wherein R.sup.3 is a C.sub.1 -C.sub.5 alkyl group, a C.sub.3 -C.sub.4 alkenyl group or a C.sub.3 -C.sub.4 alkynyl group (JP-A 61-76486).
However, there has been a great demand for further improvements in the conditions and procedures of conventional production processes to attain the production of the benzoxazine compounds (I) with high quality on an industrial scale.
For example, although the benzoxazine compounds (I) can be produced from an aniline compound of the formula: ##STR3## (JP-A 62-221677), various side reactions have a tendency to accompany this production because the aniline compound (II) has a reactive amino group. It is not always easy to produce the benzoxazine compounds (I) with high quality on an industrial scale.
Moreover, although the aniline compound (II) as their raw material can be obtained, for example, by catalytic reduction of a fluorodinitrobenzene derivative of the general formula: ##STR4## wherein X is a C.sub.1 -C.sub.5 alkoxycarbonyl group, or a carboxyl group (JP-A 62-212375), it is sometimes difficult to separate the aniline compound (II) from the catalyst used, because this compound is slightly soluble in organic solvents which have been widely used for industrial applications.